1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method whereby motion blur is added to motion images, as well as to a recording medium storing a program that causes a computer or other computational apparatus to execute such image processing.
2. Description of the Related Art
Consider a series of motion images imaged by an imaging apparatus having shutter functions, wherein the effective exposure time of each frame is short with respect to the period determined by the frame rate. When such motion images are displayed using a display device, the motion of moving objects in the motion images will be displayed in a discontinuous manner, and in some cases result in a visual reduction in picture quality wherein a viewer viewing the motion images perceives overlapping images.
Such motion image quality reduction due to unnatural motion is typically referred to as motion jerkiness, and is defined in the ANSI T1.801.02-1996 standard.
A specific example of the production of motion jerkiness will now be described with the use of the motion image imaging apparatus 500 and motion image playback apparatus 600 shown in FIG. 20.
The motion image imaging apparatus 500 images and encodes motion images according to a standard such as MPEG (Moving Picture Experts Group), and then records the encoded image data onto a recording medium 700 such as a DVD (Digital Versatile Disc).
More specifically, the motion image imaging apparatus 500 includes imaging optics 510 that focus light from the object, imaging elements 520 that receive and convert the light focused by the imaging optics 510 into an image signal, and a coding processor 530 that encodes the image signal output by the imaging elements 520.
In addition, the motion image imaging apparatus 500 is also provided with a transmit processor 540 that externally transmits image data encoded by the coding processor 530 via a transmission path, and a recording processor 550 that records image data encoded by the coding processor 530 onto a DVD or similar recording medium 700.
The imaging optics 510 include an aperture mechanism 511 that adjusts the amount of incident object light, and an optical lens system 512 that causes object light (whose amount has been adjusted by the aperture mechanism 511) to be focused onto the light-accepting surface of the imaging elements 520.
Meanwhile, the motion image playback apparatus 600 decodes encoded image data and then outputs the result to a display or similar device.
More specifically, the motion image playback apparatus 600 includes a receive processor 610 that receives encoded image data transmitted via the transmission path, and a read processor 620 that reads encoded image data from the recording medium 700.
In addition, the motion image playback apparatus 600 is also provided with a decoding processor 630 that decodes encoded image data output from the receive processor 610 and the read processor 620, as well as an output unit 640 that outputs an image signal decoded by the decoding processor 630 to a display or similar device.
When imaging motion images outdoors in a bright environment, for example, a motion image imaging apparatus 500 of the related art like that described above appropriately controls the exposure amount so as to limit the amount of light incident on the imaging elements 520 by narrowing the aperture mechanism 511.
Normally, however, the image is blurred by diffraction phenomena if the aperture mechanism 511 is excessively narrowed. For this reason, the motion image imaging apparatus 500 conducts suitable exposure control by increasing the shutter speed in addition to adjusting the amount of light by means of the aperture mechanism 511.
Exposure control is also conducted by modifying the shutter speed in motion image imaging apparatus that are not provided with aperture mechanisms.
By increasing the shutter speed in this way, the motion image imaging apparatus 500 is able to conduct suitable exposure control for outdoor imaging and similar situations.
However, when a motion image imaging apparatus 500 of the related art excessively increases the shutter speed, a phenomenon occurs wherein the image motion no longer appears smooth to the human eye.
Such picture quality reduction due to unnatural motion is typically referred to as motion jerkiness. In other words, if the motion image imaging apparatus 500 acquires motion images such that jerkiness is produced, then the motion image playback apparatus 600 will decode and display the jerky image data as-is on the output unit 640.